Telematics units within mobile vehicles provide subscribers with connectivity to a telematics service provider (TSP). The TSP provides subscribers with an array of services ranging from emergency call handling and stolen vehicle recovery to diagnostics monitoring, global navigation system aided position identification, map services, and turn-by-turn navigation assistance. Telematics units are often provisioned and activated at a point of sale when a subscriber purchases a telematics-equipped vehicle. Once provisioned and activated, telematics units can be utilized by a subscriber to obtain telematics services, such as those described herein, from the TSP.
One service provided by a TSP is Global Navigation Satellite System (GNSS) based navigation. GNSS is a generic term referring to any of multiple satellite constellation-based global positioning networks including, for example, the Global Positioning System (GPS) constellation. Another GNSS constellation network is the Global Navigation Satellite System (GLONASS). A particular example of GNSS based navigation services is the provision of turn-by-turn (TBT) directions from a current location of a vehicle (or from an alternative start location) to a specified destination location.